During the projection and scanning of films, it is possible to observe picture instabilities resulting from non-uniform transport of the film during recording and/or during projection or scanning. The picture instabilities lead to undesirable motion components which the viewer perceives as disturbing wobbling of the picture.
DE 195 36 691 has disclosed for example a method and an arrangement for correcting picture instabilities during television scanning, in which the picture component in the video signal is corrected with regard to the picture stability by a correction signal. In this case, it is specified specifically how motion vectors are derived by means of a search method which is based on the test displacement of a pattern region from one picture to the next and the determination of a correlation of the pattern region with the corresponding region of the next picture.
However, the derived motion vectors comprise both the picture instabilities and the movements that are actually present, for example movements in the recorded scene or pan movements of the camera. However, these components cannot be unambiguously separated from one another. Therefore, an exact reconstruction of the real motion sequence is not possible.
When viewing the motion present in the scanned picture, it is possible to distinguish between a still picture and a moving picture. In the case of a still picture, picture instabilities are highly pronounced even in the case of a small amplitude. The requirements made of the quality of the correction are particularly high here. The correction signal can be calculated very simply, however, for this case. In order to obtain the course of the path of a pixel, it is necessary merely to continuously sum the displacement vectors. The instantaneous position of the pixel is then obtained. For correction, said pixel is displaced from the instantaneous position to a fixed position in the picture plane.
In the case of moving pictures, picture instabilities with a small amplitude are not so highly pronounced. However, a picture stability correction must not disturb the real motion.